1. Field of the Invention
The present invention relates in general to a safety system of a passenger motor vehicle, and more particularly to an air-bag system mounted in the motor vehicle for protecting a passenger upon a vehicle collision or the like.
2. Description of the Prior Art
Hitherto, various types of air-bag systems have been proposed and put into practical use in the field of motor vehicles.
In order to clarify the task of the present invention, one of the conventional air-bag systems will be outlined with reference to FIG. 12 of the accompanying drawings.
As is shown in the drawing, the air-bag system 1 comprises an air-bag proper 3 which is folded up and mounted on a steering wheel 2. An inflator (no numeral) is also mounted on the steering wheel 2 having gas discharging openings exposed to the interior of the air-bag proper 3. Upon a vehicle collision, a deceleration sensor (not shown) issues a signal to operate the inflator. Thus, the inflator generates gas thereby to instantly inflate the air-bag proper 3 as is illustrated by a phantom line in the drawing. With this, the upper half of the driver is safely protected from being directly abutting against the rigid steering wheel 2 or windshield. Although not shown in the drawing, a relief valve is connected to the inflator, which functions to release part of the gas in the air-bag proper when, due to collision of the driver against the inflated air-bag proper, the pressure in the air-bag proper 3 exceeds a given degree. With this gas releasing, shock applied to the driver by the air-bag proper 3 is lightened. Some of the air-bag systems of this type are shown in Japanese Patent First Provisional Publication No. 47-72839 and Japanese Utility Model First Provisional Publication No. 61-117051.
Although the above-mentioned air-bag systems have provided some protection to passengers, the air-bag systems have in the past been unable to provide optimum passenger protection under vehicle collision conditions to passengers with vastly different physical features.
Furthermore, due to the force of inertia of an expanding air-bag proper, undesired rapid pressure drop tends to occur just after a rapid pressure increase upon inflation of the bag. This pressure drop delays the time at which the air-bag proper is inflated to a degree suitable for assuredly protecting the passenger.